What type of sampler is best for obtaining undisturbed samples from soft sediments?

The Shelby tube is the best choice for obtaining undisturbed samples from soft sediments because it is specifically designed to minimize disturbance during the sampling process. The Shelby tube is a thin-walled, cylindrical sampler that is pushed into the sediment under its own weight or using a hammer. Its design allows it to retrieve a core of sediment without altering the structure of the sediment layers.

The cylindrical shape and the thin walls of the Shelby tube help preserve the original sediment fabric and moisture content, which are critical for analyses that require accurate representation of the in-situ conditions. This is particularly important in geotechnical engineering and environmental studies where understanding the properties of the sediment in its undisturbed state is necessary for evaluations and modeling.

In contrast, other options like the Split Spoon sampler, while useful for obtaining samples, tend to disturb the sediment more due to their design and sampling technique. The Modified California sampler is also less effective for soft sediments due to its broader profile, which can lead to more disturbance during retrieval. Lastly, a sieve is not a sampler for collecting undisturbed samples; it is used for separating materials based on size rather than for obtaining sediment cores. Therefore, the Shelby tube stands out as the most effective option for the task of retrieving undist